PRINCIPLES OF UNIFIED SYSTEMS SAFETY ANALYSIS.

Abstract Unified Systems Safety Analysis (USSA) is a method for achieving safety control. In particular, it is a methodology for (1) interfacing safety analysis with the life cycle (concept development to system retirement) and different operating phases of a total system; and (2) logically developing a level of safety in terms of the likelihood and consequence of a specified undesired event. The principal point of view of USSA which differs from other methodologies relates to safety control. USSA has been evolved to both assess and monitor the level of safety while revealing necessary adjustments either in design, procedure, or both to sustain a prescribed level. Thus, “analysis” in reference to USSA is not to be interpreted in a passive sense as it relates to design. In particular, USSA is to effect design to the extent that design controls safety. To serve the desired monitoring function has required that particular attention be given to the effect of safety of plant operations. Thus, in the methodology considerable care has been taken to put the more analytical activities of safety analysis in context with the more routing activities of operations to assure to the extent possible their proper interaction. A successful execution of USSA depends on accurate descriptions of the systems involved, representative data, and suitable analytical techniques for implementation. The principal ingredients of USSA which are an easily understood activity network, the supporting mathematical analysis and appropriate computational schemes are covered in the present article.